NUC-1031 is a prodrug of gemcitabine developed by NuCana BioMed Ltd., and is currently in Phase II clinical trials for the treatment of cancers such as advanced solid tumors, pancreatic cancer and breast cancer. The CAS of NUC-1031 is 840506-29-8 and NUC-1031 has a structure as represented by formula 1 below, and the following formulae RP-1 and SP-1 are respectively the enantiomers of phosphorus atom P of NUC-1031:

WO2005012327 discloses a great number of phosphoramidate nucleoside prodrugs, and these phosphoramidate nucleoside prodrugs are mostly present in the form of a mixture of the enantiomers(R/S) of P. It is rather difficult to isolate a high-purity single isomer according to the conventional separation methods such as the separation by chiral column or the separation by column chromatography. As reported in the literature “Application of ProTide Technology to Gemcitabine: A Successful Approach to Overcome the Key Cancer Resistance Mechanisms Leads to a New Agent (NUC-1031) in Clinical Development” (Journal of Medicinal Chemistry, Volume 57, Issue 4, Pages 1531-1542), NUC-1031 was prepared by purification via a silica gel column, and the contents of the isomers finally obtained were 48% and 52%, respectively.
At present, the preparation methods of the single enantiomer of the phosphoramidate nucleoside prodrug P are rarely reported in the prior art. Since the two enantiomers of chiral P in this kind of molecular structure are very similar in structure and polarity, it becomes very difficult to isolate a high-purity single isomer from the racemic mixture of NUC-1031, and in particular, it is even more difficult to balance purity and yield simultaneously in the purification process.
Isolating single isomers from enantiomers, studying their biological activities respectively, and studying the pharmacological effects, toxic side effects, adverse reactions, or the like of the phosphoramidate nucleoside prodrugs to develop similar drugs with better activity and less toxic side effects will be of great significance.
The compound 61501b, when used as a key intermediate for the preparation of the single isomers of a variety of phosphoramidate nucleoside prodrugs, can significantly improve the purity of the single isomers, increase the production efficiency, reduce the production costs, and provide qualified raw materials for the clinical study of the single isomers of the phosphoramidate nucleoside prodrugs.
The CAS of the compound 61501b is 1392015-79-0, and its structure is shown as below,

In the prior art, there are few studies about the preparation methods, the crystal forms, and the like of the compound 61501b. Only the structure of the compound 61501b is disclosed in WO2012075140, but the related information about the preparation methods, the crystal forms, and the like of the compound 61501b has not been reported in any literature at present. Therefore, there is an urgent need to develop a composition containing the high-purity compound 61501b that meets the market demand and a method for preparing the high-purity compound 61501b suitable for industrial production.